1. Field of the Invention
This invention relates to panels for constructing enclosures, specifically thermal isolation enclosures and methods and systems for construction of thermally isolated enclosures, such as built-in refrigeration units, air-handling units, mechanical rooms, and HVAC enclosures.
2. Description of the Related Art
There is a general desire in industry to provide for thermal isolation of a variety of systems. Thermal isolation allows for temperature inside a housing to be manipulated independent of the temperature outside the housing. This can be valuable in places such as Heating, Ventilation, and Cooling (HVAC) systems which are intended to modify air temperature and then provide the altered air temperature to a building or other structure to regulate its internal temperature. Similarly, certain areas of a structure may comprise temperature controlled rooms. Enclosures such as walk-in refrigerators or freezers can require thermally isolated enclosures to operate efficiently and effectively,
While systems of these types seek thermal isolation because of alteration of the temperature of the air internal to the enclosure and efficiency in maintaining the air temperature, other systems seek thermal isolation for purposes beyond efficiency.
In “clean room” applications or in facilities that process food, pharmaceuticals, or other products intended for human consumption there can be concerns if temperature differentials become apparent. The internal air of these facilities often needs to be climate controlled to provide for a safe and comfortable working and processing environment. However, when there are temperature differentials at walls or other surfaces, there can be condensation from natural environmental air which can result in the introduction of chemicals to manufactured products which can be harmful to the end users.
The enclosures for HVAC, air handling, and similar system components generally share a few common features to provide for improved thermal and other factor insulation. Firstly, the enclosures are generally designed to be sealed and relatively airtight. This allows the system to prevent external air, which is not filtered and may contain contaminants and will also generally be at a different temperature, from entering the system and being used as make up air for the facility. This allows dust, pollutants, and allergens to be filtered out of the air before it is supplied to the generally enclosed environment. Further, it keeps efficiency of the system up by inhibiting temperature controlled air from not being kept segregated.
Conductive insulation and segregation has traditionally been supplied by the inclusion of insulation in the walls of the enclosure. The enclosure will generally have insulation, such as foams, spun fibers, or even air, in wall panels. The wall panels themselves are generally constructed of aluminum or a similar metal to provide for a solid, generally non-permeable, surface, Further, as many of this enclosures are located outside of the principle structure (such as on a roof) metal can provide for strong, resistant, generally weatherproof outer and inner surface to prevent damage to the insulation from exposure to the elements. Further, even on interior or partially interior installations, metal surfaces, such as aluminum or stainless steel can provide for surfaces which are readily cleaned and disinfected to provide for necessary sanitation.
In particularly demanding applications, the use of aluminum or other metal as the interior and exterior surfaces of the enclosure can result in very small “breaks” in the thermal isolation properties of the housing. In particular, the use of metal surfaces, along with the requirement to solidly connect components together such as with rivets, screws, and the like can result in their being a traceable “path” of metal through the insulation in the walls which can provide for a thermal passageway. This can result in possible condensation where metal joins the exterior and the interior of the enclosure due to a temperature differential, and can also cause decreases in efficiency.
In applications such as clean rooms, pharmaceutical, food, or microelectronic manufacturing, even a very small amount of condensation entering the environment can result in potentially catastrophic consequences due to the need to precisely control the chemical makeup of the air in these facilities, and to provide that contaminants are not introduced to the manufactured goods. These types of applications therefore focus on complete thermal isolation where there are no metal paths which can result in local temperature variations on the internal, or external, walls.
To provide for this demanding type of application, the construction of such enclosures attempts to provide a structure which is referred to as “no-through-metal” construction. A no-through-metal enclosure is constructed in such a way that there is no metal to metal connections which can be traced from metal in contact with air outside the outer surface of the enclosure to a piece of metal on the interior of the enclosure. Effectively, every path, no matter how small, needs to pass through a thermal break, or a layer of thermal insulation designed to inhibit a temperature differential from passing between the two outer walls.
The requirements of no-through-metal construction are very demanding as even standard connection components such as rivets, screws, or welds can provide the metal pathway. Further, corners, where construction techniques can require certain types of connections, can be problematic in building no-through-metal enclosures. The problem is further compounded by a desire to make construction of such enclosures modular. While modular components can provide for easier and less expensive construction, they also often require the use of more connectors and different structures which often make it hard to keep metal from providing a through path since the modular construction often provides for insulation encased in metal panels and the need to interconnect metal pieces to other metal pieces using metal connectors which can penetrate thermally insulative layers placed between them.
In order to construct no-through-metal enclosures a number of expensive and manufacturing intensive schemes have previously been used. In particular, in many such constructions connectors are entirely non metal and utilize plastic, resin, or fiber material based rivets and screws. This can be effective to create a no-through-metal structure as one of the most common sources of a metal pathway is a connector, such as a rivet, passing between two metal sheets which are otherwise separated by an insulative sheet. While effective, however, this process is often prohibitively expensive and can result in structures that are not as secure as the alternative material fasteners lack the strength of traditional metal fasteners.
Alternatively, some manufacturers use extruded components of aluminum which can then have injected therein insulative foams, resins, or other structures which serve to provide structural support and act as support beams. A portion of the aluminum can then be milled away around the hardened resin or foam to eliminate a metal path and isolate the metal components. From this type of construction, metal plates can be added either external or internal on the beams, utilizing the small resin component as a thermal break.
These devices traditionally are in the form of “I” beams or similar shapes with a specially designed void for the resin in the center of the “I”. Once the beam is formed, the center is filled with a thermal break material, such as insulating foam or resin which has sufficient structural integrity to support the remaining metal once it has hardened or cured. Once the resin is cured, strips of aluminum can be removed by processes such as milling which breaks the metal construction effectively breaking the “I” in the center providing that no metal extends across the line. The beams then are positioned to provide for the support structures for external and internal sheet metal which are attached at the top and bottom of the “I” using metal connectors but maintaining the thermal break from the resin block in the center. The resulting empty space is then filled with additional insulation.
While these structures are effective at forming no-through-metal buildings, they can very expensive to construct. In the first instance, due to their unique shape the “I” beams require the use of extruded metals, which require expensive molds and processes to form. Further, the curing and milling process is also expensive and requires additional steps in construction
For this reason, the resulting enclosures constructed using these materials are often significantly more expensive than structures which have only a very limited amount of through metal limiting their use to where such construction is absolutely necessary, and cost is effectively not a factor in determining the nature of the construction. At the same time, construction of less efficient enclosures, while often less expensive in the actual enclosure construction, results in increases in cost due to the need for the enclosure to include a safety factor which requires larger enclosures or more powerful components to compensate for leakage and poor enclosure quality without compromising the resultant air quality.